This invention relates generally to implantable medical devices and more particularly, it relates to an implantable cardiac defibrillator employing a digital waveform analyzer system for performing direct analysis of digitized ECG heart signals from the atrial and/or ventricle heart chambers, thereby relieving much of the burden of the system microprocessor in performing data analysis.
In recent years, there has been substantial progress made in the research and development of defibrillating devices for providing an effective medical response to various disorders, such as ventricular fibrillation. Research effort has also been made toward developing improved sensing techniques for reliably monitoring heart activity so as to determine whether a defibrillating high energy shock is required.
There are known in the prior art electrical cardiac defibrillators which automatically detect and analyze the electrical activity of the heart and respond to certain predetermined parameters of the QRS complexes by electrically stimulating the heart so that abnormal heart beats can be corrected. Such a prior art cardiac defibrillator is disclosed in U.S. Pat. No. 3,857,398 to Leo Rubin, wherein a heart beat analyzer-control device is utilized to analyze automatically the QRS complexes of a heart beat and, when necessary, applies proper defibrillation or pacer pulses to the heart. However, the waveforms of the heart signals in this prior art cardiac defibrillator are essentially analyzed in an analog manner. The inventors of the present invention are unaware of an implantable cardiac defibrillator having a waveform analyzer system capable of performing signal conditioning and processing of digitized ECG heart signals so as to permit direct analysis of the same by a microprocessor.
It has therefore been determined that there is a need for an implantable cardiac defibrillator employing a digitized waveform analyzer system for extracting information from digitized ECG heart signals in an efficient and effective manner to better distinguish between malignant tachyarrhythmias, such as ventricular fibrillation and normal sinus rhythm.